The present invention relates to microelectromechanical (MEM) positioning devices, and more particularly to a MEM positioning device that comprises parallelogram linkages to achieve substantially translational motion of a platform (i.e., motion in a single plane and without rotation).
Precise control of position and orientation is required for many types of m MEM device applications. An example of an application benefiting from such precise micropositioning is high-performance optical MEM laser scanner as disclosed by J. R. Wendt et al., J. Vac. Sci. Technol. B 18, 3608 (2000). In this laser scanner, a diffractive optical element is patterned on a polysilicon shuttle that is linearly translated in the plane of a substrate, thereby enabling scanning of an output laser beam. To maintain proper orientation of the diffractive optical element relative to the laser beam to be scanned, the shuttle must exhibit substantially translational motion. For the scanner disclosed by Wendt et al., linear translation was accomplished by a gear-driven rack, or by a reciprocating arm linked to a rotating gear. Other micropositioning MEM devices have been proposed to independently control the orthogonal movement of a stage in two dimensions (e.g., U.S. Pat. No. 5,962,949 to Dhuler). However, there remains a need for reliable, precise micropositioning of a platform in two orthogonal dimensions wherein orientation of the platform is maintained over a range of motion and rubbing surfaces are eliminated.
The present invention provides a MEM positioner, comprising a substrate, a moveable platform, and at least one linkage mechanism having a plurality of links, wherein the linkage mechanism is pivotably attached to the substrate by at least two anchor links and pivotably attached to the moveable platform by at least two platform links, and whereby the platform is constrained to exhibit substantially translational movement in a plane. The linkage mechanisms can be parallelogram linkages.
The MEM positioner can be actuated by a variety of means, including electrostatic, electromagnetic, piezoelectric, and thermal activation of the linkage mechanisms and/or the platform. Rotary actuation of one or more of the anchor links enables fixed location actuators and precise translational control of the platform position. Such actuation can be provided by rotary electrostatic actuators operatively connected to one or more of the anchor links.
The MEM positioner can be fabricated by a variety of device fabrication technologies generally known to those in the art, including sacrificial surface micromachining, bulk micromachining, and LIGA (LIGA is a German acronym that stands for lithography, electroplating, and molding). The MEM positioner can be formed on a silicon substrate by surface micromachining, using planar fabrication process steps known to the integrated circuit (IC) art. The platform can be formed of polycrystalline or single crystal silicon and can have a structure and properties modified for specialized applications, such as optical applications.
Advantages of the MEM positioner of the present invention include precision positioning of a moveable platform; no wear-induced change in performance, due to the absence of rubbing surfaces; inherent orientation stability due to the constrained system geometry; and extremely low hysteresis.